Load drive device

ABSTRACT

Provided is a load drive device comprising: a first input terminal for accepting an input of a first input current from a power source; a second input terminal for accepting an input of a second input current from the power source via an external resistor; an output terminal for outputting an output current to a load; a current distribution unit for summing the first input current and second input current at a prescribed distribution ratio and generating the output current and a control unit for controlling the distribution ratio. As one example, it would be appropriate for the control unit to control the distribution ratio according to the difference between a first terminal voltage present in the second input terminal and a second terminal voltage present in the output terminal.

TECHNICAL FIELD

The invention disclosed herein relates to a load drive device.

BACKGROUND ART

FIG. 17 is a diagram showing a conventional example of a semiconductorintegrated circuit device. A load drive device X of this conventionalexample is a semiconductor integrated circuit device (what is called adriver IC) which receives an input of an input voltage Vin from a powersource E and outputs an output voltage Vout and an output current Ioutto a load Z.

An example of the conventional technology related to the above isdisclosed in Patent Document 1 identified below.

CITATION LIST

Patent Document

-   Patent Document 1: Japanese Patent No. 5897768

SUMMARY OF INVENTION Technical Problem

FIG. 18 is a diagram showing the output behavior of the load drivedevice X, illustrating, in order from top to bottom, a relationshipbetween the input voltage Vin and the output voltage Vout, arelationship between the input voltage Vin and the output current Iout,and a relationship between the input voltage Vin and power consumptionPc.

As shown in the figure, the load drive device X performs, withoutdepending on the input voltage Vin, an output feedback control to keepthe output current Iout at a constant value. In the output feedbackcontrol, the output voltage Vout is determined depending on thecharacteristics of the load Z (for example, if the load Z is an LED(light emitting diode), depending on its forward voltage drop). Thepower consumption Pc is obtained as the product of the differencebetween the input and output voltages (Vin−Vout) and the output currentTout.

Accordingly, in the load drive device X, as the input voltage Vin rises,the power consumption Pc increases and also the amount of heatgeneration becomes large. Thus, for sufficient dissipation of heat fromthe load drive device X, the print-circuit board on which the load drivedevice X is mounted needs to have a large area, and this makes itdifficult to install the load drive device X in a compact module.

An object of the invention disclosed herein is, in view of the aboveproblem found by the inventors of the present application, to provide aload drive device capable of distributing power consumption in it.

Solution to Problem

A load drive device disclosed herein includes a first input terminal foraccepting an input of a first input current from a power source, asecond input terminal for accepting an input of a second input currentfrom the power source via an external resistor, an output terminal foroutputting an output current to a load, a current distributor configuredto generate the output current by summing the first input current andthe second input current at a prescribed distribution ratio, and acontroller configured to control the distribution ratio (a firstconfiguration).

Preferably, in the load drive device having the above-described firstconfiguration, the current distributor includes a first transistor in apath in which the first input current flows, and the controller isconfigured to control an on-resistance value of the first transistor (asecond configuration).

Preferably, in the load drive device having the above-described secondconfiguration, the current distributor further includes a secondtransistor in a path in which the second input current flows, and thecontroller is configured to differentially control on-resistance valuesof the first transistor and the second transistor (a thirdconfiguration).

Preferably, in the load drive device having any one of the first tothird configurations described above, the controller is configured tocontrol the distribution ratio according to a difference value between afirst terminal voltage appearing at the second input terminal and asecond terminal voltage appearing at the output terminal (a fourthconfiguration).

Preferably, in the load drive device having the fourth configurationdescribed above, the controller includes an input detector configured togenerate a first differential input voltage from the first terminalvoltage, an output detector configured to generate a second differentialinput voltage from the second terminal voltage, and a differentialamplifier configured to generate a control signal for the currentdistributor according to a difference value between the firstdifferential input voltage and the second differential input voltage (afifth configuration).

Preferably, in the load drive device having the fifth configurationdescribed above, the input detector is configured to generate the firstdifferential input voltage by subtracting a prescribed threshold voltagefrom the first terminal voltage (a sixth configuration).

Preferably, in the load drive device having the fifth or sixthconfiguration described above, the output detector is configured tooutput a highest value of a plurality of the second terminal voltages asthe second differential input voltage (a seventh configuration).

Preferably, in the load drive device having the fifth or sixthconfiguration described above, the output detector is configured tooutput an average value of a plurality of the second terminal voltagesas the second differential input voltage (an eighth configuration).

Preferably, in the load drive device having any one of the first tothird configurations described above, the controller is configured tocontrol the distribution ratio according to a difference value between aterminal voltage appearing at the second input terminal and a prescribedreference voltage (a ninth configuration).

Preferably, the load drive device having any one of the first to ninthconfigurations described above further includes a current driverconfigured to perform constant current control of the output current (atenth configuration).

Preferably, in the load drive device having the tenth configurationdescribed above, the current distributor is integrated on a first-sideside of the semiconductor chip, and the current driver is integrated ona second-side side of the semiconductor chip opposite to the first-sideside of the semiconductor chip (an eleventh configuration).

Preferably, in the load drive device having the eleventh configurationdescribed above, the current driver includes a plurality of constantcurrent sources respectively connected between the current distributorand a plurality of the output terminals (a twelfth configuration).

Preferably, in the load drive device having the twelfth configurationdescribed above, in plan view of the semiconductor chip, the pluralityof constant current sources are arranged in a direction along the secondside of the semiconductor chip (a thirteenth configuration).

Preferably, in the load drive device having the thirteenth configurationdescribed above, in plan view of the semiconductor chip, the currentdistributor is integrated between a position adjacent to such a constantcurrent source of the plurality of constant current sources as islocated closest to a third side of the semiconductor chip and a positionadjacent to such a constant current source of the plurality of constantcurrent sources as is located farthest from the third side of thesemiconductor chip (a fourteenth configuration).

Preferably, in the load drive device having any one of the first tofourteenth configurations described above, a terminal connected to thepower source and a terminal adjacent to the terminal have withstandvoltages sufficient to withstand connection to the power source (afifteenth configuration).

Preferably, in the load drive device having the second configurationdescribed above, the first transistor includes a source region, a sourcepad provided immediately close to the source region and wirebonded tothe first input terminal, a drain region, and a drain pad providedimmediately close to the drain region and wirebonded to the second inputterminal (a sixteenth configuration).

Preferably, in the load drive device having any one of the first tosixteenth configurations described above, the first input terminal andthe second input terminal are arranged adjacent to each other (aseventeenth configuration).

Preferably, in the load drive device having any one of the first toseventeenth configurations described above, an external terminaldesignable to have a high withstand voltage more easily than otherexternal terminals is arranged adjacent to the first input terminal orthe second input terminal (an eighteenth configuration).

Preferably, in the load drive device having any one of the first toeighteenth configurations described above, the first input terminalaccepts the input of the first input current directly from the powersource (a nineteenth configuration).

Preferably, in the load drive device having any one of the first tonineteenth configurations described above, the controller is configuredto dynamically control the distribution ratio (a twentiethconfiguration).

Preferably, in the load drive device having any one of the first totwentieth configurations described above, the load drive device isintegrated in a semiconductor device (a twenty-first configuration).

Preferably, in the load drive device having the second configurationdescribed above, the controller is configured to dynamically control theon-resistance value of the first transistor (a twenty-secondconfiguration).

Preferably, in the load drive device having the third configurationdescribed above, the controller is configured to dynamicallydifferentially control the on-resistance value of each of the firsttransistor and the second transistor (a twenty-third configuration).

Preferably, in the load drive device having the fourth configurationdescribed above, the controller is configured to dynamically control thedistribution ratio according to the difference value between the firstterminal voltage and the second terminal voltage (a twenty-fourthconfiguration).

An electric appliance disclosed herein includes the load drive devicehaving any one of the first to twenty-fourth configurations describedabove, an external resistor connected between a first input terminal anda second input terminal of the load drive device, and a load connectedto an output terminal of the load drive device (a twenty-fifthconfiguration).

A lamp module disclosed herein includes the load drive device having anyone of the first to twenty-fourth configurations, an external resistorconnected between a first input terminal and a second input terminal ofthe load drive device, and a light source connected as a load to anoutput terminal of the load drive device (a twenty-sixth configuration).

A vehicle disclosed herein includes the lamp module having thetwenty-sixth configuration described above, and a battery as a powersource for the lamp module (a twenty-seventh configuration).

Preferably, in the vehicle having the twenty-seventh configurationdescribed above, the lamp module is a headlamp module, a rear-lampmodule, or a blinker-lamp module (a twenty-eighth configuration).

Advantageous Effects of Invention

According to the invention disclosed herein, it is possible to provide aload drive device capable of distributing power consumption in it.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an overall configuration of an electricappliance including a load drive device;

FIG. 2 is a diagram showing a first embodiment of an LED driver IC;

FIG. 3 is a diagram showing an example of power consumption distributioncontrol performed in the first embodiment;

FIG. 4 is a diagram showing a second embodiment of an LED driver IC;

FIG. 5 is a diagram showing an example of power consumption distributioncontrol performed in the second embodiment;

FIG. 6 is a diagram showing a third embodiment of an LED driver IC;

FIG. 7 is a diagram showing an example of power consumption distributioncontrol performed in the third embodiment;

FIG. 8A is a diagram showing an arrangement of terminals (16 pins) in anLED driver IC (a first example);

FIG. 8B is a diagram showing an arrangement of terminals (16 pins) in anLED driver IC (a second example);

FIG. 8C is a diagram showing an arrangement of terminals (16 pins) in anLED driver IC (a third example);

FIG. 8D is a diagram showing an arrangement of terminals (16 pins) in anLED driver IC (a fourth example);

FIG. 9 is a diagram showing a first layout in a semiconductor chip;

FIG. 10 is a diagram showing a second layout in a semiconductor chip;

FIG. 11 is a diagram showing a third layout in a semiconductor chip;

FIG. 12 is a diagram showing a fourth layout in a semiconductor chip;

FIG. 13 is a diagram showing an arrangement of pads in a currentdistributor;

FIG. 14 is a diagram showing an arrangement of terminals (7 pins) in anLED driver IC;

FIG. 15 is an external view of a motorcycle;

FIG. 16 is an external view of a four-wheeled automobile;

FIG. 17 is a diagram showing a conventional example of a load drivedevice; and

FIG. 18 is a diagram showing an example of an output behavior observedin the conventional example.

DESCRIPTION OF EMBODIMENTS

<Electronic Appliance>

FIG. 1 is a diagram showing an overall configuration of an electricappliance including a load drive device. An electric appliance 1 of thisconfiguration example has a load drive device 100, an external resistorR, and a load Z, the load drive device 100 and the external resistor Rbeing externally connected to the load drive device 100.

The load drive device 100 is a semiconductor integrated circuit device(what is called a driver IC) which receives an input of an input voltageVin from a power source E and outputs an output voltage Vout and anoutput current Iout to the load Z, and, for establishing electricalconnection with outside, the load drive device 100 has a first inputterminal INL a second input terminal IN2, and an output terminal OUT.Needless to say, the load drive device 100 may be provided with moreexternal terminals, as necessary, in addition to those mentioned above.

A first end of the external resistor R is connected to a positive end(=an input-voltage-Vin application end) of the power source E and to thefirst input terminal IN1 of the load drive device 100. A negative end ofthe power source E is connected to a ground end. A second end of theexternal resistor R is connected to the second input terminal IN2 of theload drive device 100. In this manner, the external resistor R isconnected between the first and second input terminals IN1 and IN2 ofthe load drive device 100. Here, the load drive device 100 and theexternal resistor R may both be mounted on one common printed circuitboard, or may be mounted on separate printed circuit boards one by one.Further, the external resistor R is not necessarily be a single resistorelement, but instead may be composed of a plurality of resistor elementsconnected in series or in parallel with each other.

A first end of the load Z is connected to the output terminal OUT (=anoutput-voltage-Vout application end) of the load drive device 100. Asecond end of the load Z is connected to a ground end.

<Load Drive Device>

Still with reference to FIG. 1, a description will be given of aninternal configuration of the load drive device 100. The load drivedevice 100 has, in addition to the first input terminal IN1, the secondinput terminal IN2, and the output terminal OUT mentioned above, acurrent distributor 110, a controller 120, and a current driver 130integrated in it.

The first input terminal IN1 is an external terminal for accepting aninput of a first input current Iin1 directly from the power source E.

The second input terminal IN2 is an external terminal for accepting aninput of a second input current Iin2 from the power source E via theexternal resistor R.

The output terminal OUT is an external terminal for outputting theoutput voltage Vout and the output current Iout to the load Z.

The current distributor 110, based on a control signal Sc from thecontroller 120, sums the first input current Iin1 and the second inputcurrent Iin2 at a prescribed distribution ratio to generate the outputcurrent Iout.

The controller 120 continuously detects the difference value Vx−Vy(corresponding to the voltage drop between the input and outputterminals) between a first terminal voltage Vx appearing at the secondinput terminal IN2 and a second terminal voltage Vy appearing at theoutput terminal OUT, and dynamically controls the aforementioneddistribution ratio by generating the control signal Sc such that thedetected value does not exceed a prescribed upper limit value.Specifically, until the difference value Vx−Vy reaches the prescribedupper limit value, basically only the first input current Iin1 is passedand the second input current Iin2 is cut off; on the other hand, afterthe difference value Vx−Vy has reached the prescribed upper limit value,the aforementioned distribution ratio is automatically and smoothlyadjusted so as to reduce the first input current Iin1 and to increasethe second input current Iin2. Here, as to the detection of the secondterminal voltage Vy, a modification is possible where it is omitted.Such a modified example will be dealt with in connection with a thirdembodiment (FIG. 6), which will be described later.

The current driver 130 performs constant current control of the outputcurrent Iout. That is, the current driver 130 performs, withoutdepending on the input voltage Vin, an output feedback control of theoutput current Iout to keep the output current Iout at a constant value.

Thus, the load drive device 100 of this configuration example has afunction (hereinafter referred to as “the power consumption distributionfunction”) of, at a time of the input voltage Vin rising, intentionallycreating, by, for example, using the external resistor R providedoutside the device (an input side), a loss of part of excessive powerconventionally consumed inside the device.

The adoption of this configuration makes it possible to keep the powerconsumption inside the device constantly at or lower than a prescribedupper limit value, and thus to reduce heat generation in the load drivedevice 100. This provides a sufficient margin in the allowable powerdissipation of the load drive device 100, and thus the load drive device100 does not need to be mounted on an unnecessarily large printedcircuit board and can be easily installed in a compact module.

Moreover, the input dynamic range of the load drive device 100 (=therange of the input voltage Vin that can be fed to the load drive device100) is also widened, and thus, for example, a battery which provides anunstable input voltage Vin can be used as the power source E.

Furthermore, with the load drive device 100 of this configurationexample, inside which no excessive power is applied, it is possible toreduce stress on internal elements, and thus to contribute to higherreliability and a longer product life.

The external resistor R is a discrete element and is more heat-resistantthan the load drive device 100 which is a semiconductor device, and thusheat generation to some extent will cause no particular damage to theexternal resistor R.

Hereinafter, in connection with various embodiments, more specificdescriptions will be given, dealing with examples of application to amulti-channel LED driver IC.

First Embodiment

FIG. 2 is a diagram showing a first embodiment of an LED driver IC. Inthis embodiment, the electric appliance 1 described previously isconfigured as an LED lamp module, and the load drive device 100 isconfigured as a four-channel LED driver IC provided with outputterminals OUT1 to OUT4. As the power source E, a battery is used, and,as the load Z, an LED light source is used which is provided with LEDstrings Z1 to Z4 arranged in parallel with each other.

Thus, in the following description, the electric appliance 1, the loaddrive device 100, the power source E, and the load Z will be read as anLED lamp module 1, an LED driver IC 100, a battery E, and an LED lightsource Z, respectively, and they will be described in detail.

The LED driver IC 100, together with the LED light source Z as itsdriving target, may be provided as the LED lamp module 1, or may beprovided as a separate IC independent of the LED light source Z.

First, a current distributor 110, among the components of the LED driverIC 100, will be described. The current distributor 110 includesP-channel MOS (metal oxide semiconductor) field-effect transistors 111and 112 as means for performing dynamic differential control of thedistribution ratio between the first input current Iin1 and the secondinput current Iin2. The transistor 111 corresponds to a first transistorprovided in a path (=direct path) in which the first input current Iin1flows. On the other hand, the transistor 112 corresponds to a secondtransistor provided in a path (=a loss path) in which the second inputcurrent Iin2 flows.

Now, a specific description will be given of the interconnection amongthem. The source and the back gate of the transistor 111 are connectedto the first input terminal IN1 (=a first input current-Iin1 input end).The source and the back gate of the transistor 112 are connected to thesecond input terminal IN2 (=a second input current-Iin2 input end). Thedrains of the transistors 111 and 112 are connected with each other, andthe connection node between them is connected, as an output current-Ioutoutput end, to the current driver 130 on a latter stage.

The gate of the transistor 111 receives a first control signal Sc1.Accordingly, as the first control signal Sc1 becomes higher, theon-resistance value of the transistor 111 becomes larger and the firstinput current Iin1 decreases. Reversely, as the first control signal Sc1becomes lower, the on-resistance value of the transistor 111 becomessmaller and the first input current Iin1 increases.

On the other hand, the gate of the transistor 112 receives a secondcontrol signal Sc2. Accordingly, as the second control signal Sc2becomes higher, the on-resistance value of the transistor 112 becomeslarger and the second input current Iin2 decreases. Reversely, as thesecond control signal Sc2 becomes lower, the on-resistance value of thetransistor 112 becomes smaller and the second input current Iin2increases.

Between the gate and the source of each of the transistors 111 and 112,a voltage clamping element may be connected.

Next, the controller 120 will be described. The controller 120 includesan input detector 121, an output detector 122, and a differentialamplifier 123, and generates, as the aforementioned control signal Sc,the first control signal Sc1 and the second control signal Sc2 tothereby perform dynamic differential control of the on-resistance valuesof the transistors 111 and 112.

The input detector 121 includes a resistor 121 a and a current source121 b which are connected in series between the second input terminalIN2 and a ground end, and generates a first differential input voltageVx′ (=Vx−Vth) by subtracting a prescribed threshold voltage Vth (=avoltage appearing across the resistor 121 a) from the first terminalvoltage Vx appearing at the second input terminal IN2. To adjust thethreshold voltage Vth as desired, it is preferable, for example, to usea variable current source as the current source 121 b.

The output detector 122 generates a second differential input voltageVy′ from second terminal voltages Vy1 to Vy4 (corresponding to theaforementioned second terminal voltage Vy) appearing at the outputterminals OUT1 to OUT4, respectively. The second terminal voltages Vy1to Vy4 are determined depending on the forward voltage drops of the LEDstrings Z1 to Z4, respectively.

Preferably, for example, the output detector 122 is configured to outputthe highest value of the second terminal voltages Vy1 to Vy4 as thesecond differential input voltage Vy′. In such a configuration, theaforementioned power consumption distribution function stays off untilthe first differential input voltage Vx′ reaches the largest of thesecond terminal voltages Vy1 to Vy4. Accordingly, even if the LEDstrings Z1 to Z4 have different numbers of series-connected LED stagesor different forward voltage drops, it is possible to securely turn onall of the LED strings Z1 to Z4.

Or, for example, the output detector 122 may be configured to output theaverage value of the second terminal voltages Vy1 to Vy4 as the seconddifferential input voltage Vy′. In such a configuration, theaforementioned power consumption distribution function is turned on at atime point that the first differential input voltage Vx′ has reached theaverage value of the second terminal voltages Vy1 to Vy4. Accordingly,even if the LED strings Z1 to Z4 have different numbers ofseries-connected LED stages or different forward voltage drops, the LEDstrings Z1 to Z4 are each unlikely to receive an excessive voltage.

The differential amplifier 123 generates the first control signal Sc1and the second control signal Sc2 according to the difference valueVx′−Vy′ between the first differential input voltage Vx′ fed to itsnon-inverting input terminal (+) and the second differential inputvoltage V′ fed to its inverting input terminal (−). A static electricityprotection device may be connected to the input stage of thedifferential amplifier 123.

Now, a specific description will be given of the operation of thedifferential amplifier 123. When Vx′−Vy′≤0 (that is, Vx−Vy≤Vth) holds,the first control signal Sc1 output from the inverting output terminal(−) of the differential amplifier 123 stays at low level, and the secondcontrol signal Sc2 output from the non-inverting output terminal (+) ofthe differential amplifier 123 stays at high level. Accordingly, in thecurrent distributor 110, the transistor 111 is fully on and thetransistor 112 is fully off, that is, only the first input current Iin1in the direct path is passed and the second input current Iin2 in theloss path is cut off.

On the other hand, when Vx′−Vy′>0 (that is, Vx−Vy>Vth) holds, the firstcontrol signal Sc1, having stayed at low level, rises from low level,and the second control signal Sc2, having stayed at high level, lowersfrom high level, and thus the on-resistance value of the transistor 111is raised from its lowest value and the on-resistance value of thetransistor 112 is lowered from its highest value. As a result, in thecurrent distributor 110, the distribution ratio between the first inputcurrent Iin1 and the second input current Iin2 is automatically andsmoothly adjusted so as to reduce the first input current Iin1 and toincrease the second input current Iin2.

In this manner, in the controller 120, the distribution ratio betweenthe first input current Iin1 and the second input current Iin2 isdynamically differentially controlled according to the difference valueVx−Vy between the first terminal voltage Vx and the second terminalvoltage Vy.

Next, the current driver 130 will be described. The current driver 130includes constant current sources 131 to 134 connected in parallel witheach other. The constant current sources 131 to 134 generate prescribedconstant currents I1 to I4, respectively, and output the constantcurrents to the output terminals OUT1 to OUT4, respectively.Accordingly, the output current Iout fed from the current distributor110 to the current driver 130 is a sum current (Iout=I1+I2+I3+I4)resulting from summing up all the constant currents I1 to I4. Althoughnot clearly shown in this figure, the current driver 130 may include alogic unit or the like as the leading agent to perform the outputfeedback control of the constant currents I1 to I4.

FIG. 3 is a diagram showing an example of power consumption distributioncontrol in the LED driver IC 100 of the first embodiment (FIG. 2),illustrating, in order from top to bottom, a relationship between theinput voltage Vin and various voltages (Vx, Vy), a relationship betweenthe input voltage Vin and various currents (Iin1, Iin2, Iout), and arelationship between the input voltage Vin and various powerconsumptions (Pc1, Pc2, Pc). Here, Pc1 represents the internal powerconsumption, which is the amount of power consumed in the LED driver IC100, and Pc2 represents the external power consumption, which is theamount of power consumed in the external resistor R. Pc represents theconventional power consumption (=corresponding to the internal powerconsumption in a case where the power consumption distribution controlis not performed).

In a first voltage range (0≤Vin<V11), as the input voltage Vin rises,the first terminal voltage Vx and the second terminal voltage Vy bothrise. In the first voltage range, however, the second terminal voltageVy does not exceed the forward voltage drop of the LED light source Z(more precisely, the lowest value of the forward voltage drops of theLED strings Z1 to Z4), the output current Tout does not flow.Accordingly, the first input current Iin1 and the second input currentIin2 both stay at the zero value, and the internal power consumption Pc1and the external power consumption Pc2 also stay at the zero value.

In a second voltage (V11≤Vin<V12), the second terminal voltage Vybecomes higher than the forward voltage drop of the LED light source Z,and the output current Tout starts to increase. In the second voltagerange, however, Vx−Vy<Vth holds, and thus the power consumptiondistribution function does not work, and the second input current Iintdoes not flow. Accordingly, the output current Tout is generatedentirely from the first input current Iint. As a result, the internalpower consumption Pc1 starts to increase, but the external powerconsumption Pc2 is kept at the zero value.

In a third voltage range (V12≤Vin<V13), the output current Tout reachesits target value (for example, 450 mA) and the second terminal voltageVy stops rising, and thus, as the input voltage Vin rises, thedifference between the first terminal voltage Vx and the second terminalvoltage Vy starts to increase. However, in the third voltage range,Vx−Vy<Vth still holds, and thus, as in the second voltage rangedescribed above, the power consumption distribution control does notwork, and the second input current Iin2 does not flow. Accordingly, theinternal power consumption Pc1 further increases, but on the other hand,the external power consumption Pc2 is kept at the zero value.

In a fourth voltage range (V13≤Vin<V14), Vx−Vy>Vth holds, and the powerconsumption distribution function starts to work. More specifically, inthe fourth voltage range, the transistors 111 and 112 operate so as tomake Vx−Vy=Vth hold, and the distribution ratio between the first inputcurrent Iin1 and the second input current Iin2 is automatically andsmoothly adjusted such that as the input voltage Vin becomes higher, thefirst input current Iin1 is reduced and the second input current Iin2 isincreased.

The provision of such power consumption distribution function makes itpossible to intentionally create, as the power consumption Pc2, a lossof part of excessive power supplied from the battery E. This makes itpossible to keep the internal power consumption Pc1 substantially at aconstant value (about one sixth of the conventional value), and thus todownsize the printed circuit board on which the LED driver IC 100 ismounted and to obtain a large output current from the LED driver IC 100.

In particular, in the LED lamp module 1 for which the power source isthe battery E, the input voltage Vin is likely to become unstable andthe allowable power dissipation of the LED driver IC 100 is highlylikely to be exceeded, and thus it is very advantageous to regulate theinternal power consumption Pc1 by the power consumption distributionfunction.

As shown in this figure, the characteristics of the output current Ioutgenerated by summing the first input current Iin1 and the second inputcurrent Iin2 are equivalent to those of the conventional example (FIG.18). Accordingly, in introducing the power consumption distributionfunction, there is no need of redesigning the current driver 130.

Second Embodiment

FIG. 4 is a diagram showing a second embodiment of an LED driver IC.Although this embodiment is based on the above-described firstembodiment (FIG. 2), in the LED driver IC 100 of this embodiment, thetransistor 112 of the current distributor 110 is omitted, and thus thecontroller 120 dynamically controls the on-resistance value of thetransistor 111 by using only the first control signal Sc1. According tothis configuration, it is possible to implement the power consumptiondistribution function substantially equal to that of the firstembodiment in a simple manner.

FIG. 5 is a diagram showing an example of power consumption distributioncontrol performed in the LED driver IC 100 of the second embodiment, andillustrates, as in FIG. 3, in order from top to bottom, a relationshipbetween the input voltage Vin and various voltages (Vx, Vy), arelationship between the input voltage Vin and various currents (Iin1,Iin2, Iout), and a relationship between the input voltage Vin andvarious power consumptions (Pc1, Pc2, Pc).

The basic operation of this embodiment is performed in the same manneras described previously, and can be understood simply by reading thevoltage values V11 to V14 in FIG. 3 as the voltage values V21 to V24,respectively, in this figure.

Since the transistor 112 is omitted in the LED driver IC 100 of thisembodiment, even in an input voltage range (V21<Vin<V23) in which thepower consumption distribution function does not work, the second inputcurrent Iin2 flows in the loss path, by which amount the first inputcurrent Iin1 decreases.

However, by setting the resistance value of the external resistor R at asufficiently large value (about 10Ω) with respect to the on-resistancevalue (about 0.5Ω) of the transistor 111 when it is fully on, it ispossible to make the second input current Iin2 sufficiently low, andthus no trouble occurs in the operation of the LED driver IC 100.

Third Embodiment

FIG. 6 is a diagram showing a third embodiment of an LED driver IC.Although this embodiment is based on the above-described firstembodiment (FIG. 2), in the LED driver IC 100 of this embodiment, theinput detector 121 and the output detector 122 of the controller 120 areboth omitted, and thus the controller 120 dynamically controls thedistribution ratio between the first input current Iin1 and the secondinput current Iin2 according to the difference value Vx−Vref between thefirst terminal voltage Vx and a prescribed reference voltage Vref.According to this configuration, it is possible to implement the powerconsumption distribution function substantially equal to that of thefirst embodiment in a simple manner.

Here, the reference voltage Vref can be set at a voltage value that ishigher than the expected value of the second terminal voltage Vy by thethreshold voltage Vth mentioned previously.

FIG. 7 is a diagram showing an example of power consumption distributioncontrol performed in the LED driver IC 100 of the third embodiment, andillustrates, as in FIG. 3, in order from top to bottom, a relationshipbetween the input voltage Vin and various voltages (Vx, Vy), arelationship between the input voltage Vin and various currents (Iin1,Iin2, Iout), and a relationship between the input voltage Vin andvarious power consumptions (Pc1, Pc2, Pc).

The basic operation of this embodiment is performed in the same manneras described previously, and can be understood simply by reading thevoltage values V11 to V14 in FIG. 3 as the voltage values V31 to V34,respectively, in this figure.

However, in the LED driver IC 100 of this embodiment, the powerconsumption distribution function is turned on/off based not on theresult of comparison between the difference value Vx−Vy and thethreshold voltage Vth but on the result of comparison between the firstterminal voltage Vx and the reference voltage Vref. Accordingly,“Vx−Vy<Vth” in the description of the first embodiment should be read as“Vx<Vref”, and “Vx−Vy>Vth” in the description of the first embodimentshould be read as “Vx>Vref”.

Further, the example dealt with in this embodiment is based on the firstembodiment (FIG. 2), but it may be based on the second embodiment (FIG.4) instead. Specifically, in the LED lamp module 1 of this embodiment,the transistor 112 of the current distributor 110 may further beomitted.

<Arrangement of Terminals (16 Pins)>

FIG. 8A to FIG. 8D are diagrams showing arrangements of terminals (16pins) in the LED driver IC 100. In each of the diagrams, in the LEDdriver IC 100, a 16-pin HTS SOP (heat-sink thin shrink small outlinepackage) is adopted as the package. This package has a total of 16 pinsdrawn out of its two opposite sides in two directions (left and rightdirections on the drawing sheet) such that eight pins are arranged oneach of the two opposite sides. Hereinafter, arrangements of terminalswill be described with reference to FIG. 8A basically.

A VINRES terminal (pin 1) is a power distribution resistor connectionterminal, and corresponds to the aforementioned second input terminalIN2. A VIN terminal (pin 2) is a source voltage input terminal, andcorresponds to the aforementioned first input terminal IN1. A PBUSterminal (pin 3) is an abnormal-state flag outputting/output-current offcontrol inputting terminal. A CRT terminal (pin 4) and a DISC terminal(pin 5) are CR timer setting terminals. An MSET1 terminal (pin 6) and anMSET2 terminal (pin 11) are mode setting terminals. A SET1 terminal (pin7), a SET2 terminal (pin 8), a SET3 terminal (pin 10), and a SET4terminal (pin 9) are output-current setting terminals for four channels.A GND terminal (pin 12) is a ground terminal. An OUT1 terminal (pin 16),an OUT2 terminal (pin 15), an OUT3 terminal (pin 14), and an OUT4terminal (pin 13) are current output terminals for four channels. AnEXP-PAD terminal, indicated by a broken line, functions as a heatdissipation pad.

Preferably, the VINRES terminal and the VIN terminal are arrangedadjacent to each other as shown in FIG. 8A to FIG. 8D. However, as canbe understood from comparison between FIG. 8A and FIG. 8B (or FIG. 8D),these two terminals may be arranged in the reverse order. Likewise,preferably, the CRT terminal and the DISC terminal are arranged adjacentto each other as shown in FIG. 8A to FIG. 8D. However, as can beunderstood from comparison between FIG. 8A and FIG. 8C (or FIG. 8D),these two terminals may be arranged in the reverse order.

The above-described four external terminals (VINRES, VIN, CRT, and DISC)are all connected to the power source E (a battery). Accordingly, it isdesirable to design these four external terminals (VINRES, VIN, CRT, andDISC) to have higher withstand voltages than the other externalterminals so that they can withstand connection to the power source E.

On the other hand, the external terminals (PBUS, GND, MSET1 and MSET2,SET1 to SET4, and OUT1 to OUT4) other than the above-described fourexternal terminals are not connected to the power source E. Accordingly,it is basically sufficient for these external terminals (PBUS, GND,MSET1 and MSET2, SET1 to SET4, and OUT1 to OUT4) to be designed to havelower withstand voltages than the other external terminals.

However, as to the external terminals (PBUS, MSET1), which are adjacentto the four external terminals (VINRES, VIN, CRT, and DISC) mentionedabove, it is desirable, as a measure against a short circuit betweenadjacent terminals, to design the external terminals (PBUS, MSET1) so asto have higher withstand voltages than the other external terminals.

That is, it is desirable to select, as an external terminal to bearranged adjacent to the four external terminals (VINRES, VIN, CRT, andDISC) mentioned above, an external terminal (for example, PBUS, MSET1,or MSET2) that is comparatively easy to design to have a high withstandvoltage.

<Chip Layout>

FIG. 9 to FIG. 12 are diagrams showing examples of layout in asemiconductor chip sealed in the LED driver IC 100. A semiconductor chip200 is a member cut out in a rectangular shape in plan view, and hasintegrated therein, besides the current distributor 110, the controller120 and the current driver 130, which have been described previously, acurrent setter 140, which is configured to set the constant currents I1to I4 for the channels, and an other-circuit portion 150 (including areference power supply, a CR timer, a protect bus controller, andvarious protection circuits, etc.).

In the following description, of the four sides constituting the outeredge of the semiconductor chip 200, the left side on the drawing sheetis defined as a first side 201, the right side, which is opposite to thefirst side 201, is defined as a second side 202, the upper side isdefined as a third side 203, and the lower side, which is opposite tothe third side 203, is defined as a fourth side 204.

In this layout, the current distributor 110 is integrated, in plan viewof the semiconductor chip 200, on the first-side-201 side of thesemiconductor chip 200 (=closer to the first side 201 than the currentdriver 130). In this layout, a pad P11 (=corresponding to the source padof the transistor 111 wirebonded to the first input terminal IN1) of thecurrent distributor 110 is provided close to the first side 201, and apad P12 (=corresponding to the drain pad of the transistor 111wirebonded to the second input terminal IN2) is provided close to thethird side 203. Such an arrangement of pads will be described later indetail.

On the other hand, in the present layout, the current driver 130 isintegrated, in plan view of the semiconductor chip 200, on thesecond-side-202 side of the semiconductor chip 200 (=closer to thesecond side 202 than the current distributor 110).

That is, the current distributor 110 and the current driver 130 arearranged separate from each other, on the first-side-201 side and on thesecond-side-202 side, respectively, of the semiconductor chip 200.

The adoption of such a chip layout makes it possible to gatherpower-input side pins (for example, pins 1, 2, 4, and 5 in FIG. 8) ofthe plurality of pins provided in the LED driver IC 100 on thefirst-side-201 side of the semiconductor chip 200 to extend in a firstdirection and gather power-output side pins (for example, pins 13 to 16in FIG. 8) on the second-side-202 side of the semiconductor chip 200 toextend in a second direction which is a direction opposite to the firstdirection. As a result, conductors connected to the power-input sidepins and conductors connected to the power-output side pins do notintersect each other, and this makes it possible to simplify the layoutin the PCB (printed circuit board) on which the LED driver IC 100 ismounted.

Further, as shown also in FIG. 2 referred to previously, for example,the current driver 130 includes the constant current sources 131 to 134respectively connected between the current distributor 110 and theoutput terminals OUT1 to OUT4. In particular, in the present layout, theconstant current sources 131 to 134 are arranged in a direction (=X-axisdirection) that is along the second side 202 in plan view of thesemiconductor chip 200. Here, pads P31 to P34 (=output pads respectivelywirebonded to the output terminals OUT1 to OUT4) of the constant currentsources 131 to 134, respectively, are all provided close to the secondside 202. Further, as shown in FIG. 12, the other-circuit portion 150may be laid between the constant current sources 131 to 134.

Here, preferably, in plan view of the semiconductor chip 200, thecurrent distributor 110 is integrated at a position between a position(see FIG. 9) adjacent to the constant current source 131 which islocated closest to the third side 203 of the semiconductor chip 200 anda position (see FIG. 11) adjacent to the constant current source 134which is located farthest from the third side 203, and it is desirablethat the current distributor 110 be integrated close to the centerposition (see FIG. 10, FIG. 12) between two opposite ends of theconstant current sources 131 to 134 in the direction (the x-axisdirection) in which they are arranged.

In particular, according to the layouts shown in FIG. 10 and FIG. 12, incomparison with the layouts shown in FIG. 9 and FIG. 11, as to theresistance component of a conductor L1 laid from the current distributor110 through the constant current sources 131 to 134, it is possible toreduce its maximum value (=the conductor resistance to such one of theconstant current sources as is located farthest from the currentdistributor 110).

For example, with the layout shown in FIG. 9, it is possible to minimizethe conductor resistance to the constant current source 131, which isadjacent to the current distributor 110, but the current resistance tothe constant current source 134, which is farthest from the currentdistributor 110, becomes very large. On the other hand, with the layoutshown in FIG. 11, it is possible to minimize the conductor resistance tothe constant current source 134, which is adjacent to the currentdistributor 110, but the conductor resistance to the constant currentsource 131, which is farthest from the current distributor 110, becomesvery large.

In contrast, with the layouts shown in FIG. 10 and FIG. 12, the lengthof the conductor from the current distributor 110 to the constantcurrent sources 131 and 134, which are farthest from the conductorcurrent distributor 110, can be reduced, and thus the conductorresistance to them can also be reduced.

The LED driver IC 100 is required to have as small an input-outputvoltage as possible. For this purpose, it is important to lower theon-resistance of the transistor 111 (or 112) constituting the currentdistributor 110, and further, to reduce the conductor resistance to aconstant current source that is farthest from the current distributor110. Thus, it can be said that it is desirable to adopt the layout shownin FIG. 10 or FIG. 12 among those shown in FIG. 9 to FIG. 12.

<Arrangement of Pads>

FIG. 13 is a diagram showing an arrangement of pads in the currentdistributor 110 (=the transistor 111) shown in FIG. 4. As shown in thisfigure, the transistor 111 includes a source region S, a source pad P11which is provided immediately close to the source region S and is bondedto the VIN terminal (=the first input terminal IN1) via a wire W1, adrain region D, and a drain pad P12 which is provided immediately closeto the drain region D and is bonded to the VINRES terminal (=the secondinput terminal IN2) via a wire W2.

Thus, as to the source pad P11 and the drain pad P12 of the transistor111, it is desirable that, without laying unnecessarily long conductorinside the semiconductor chip 200, the two pads be respectively providedimmediately close to the source region S and the drain region D andwirebonded to lead frames (=the VIN terminal and the VINRES terminal).

<Arrangement of Terminals (7 Pins)>

FIG. 14 is a diagram showing an arrangement of terminals (7 pins) in theLED driver IC 100. FIG. 8 referred to previously shows 16-pin HTSSOPpackages as examples, but when the number of output channels is small,as shown in this figure, it is possible to adopt a package having pinsdrawn out only in one direction.

Here, a SET1 terminal (pin 1) and a SET2 terminal (pin 2) areoutput-current setting terminals for two channels. An OUT1 terminal (pin3) and an OUT2 terminal (pin 4) are current output terminals for twochannels. A GND terminal (pin 5) is a ground terminal. An IN1 terminal(pin 6) is a source voltage input terminal, and corresponds to theaforementioned first input terminal IN1. An IN2 terminal (pin 7) is apower-distribution-resistor connection terminal, and corresponds to theaforementioned second input terminal IN2.

Preferably, the IN1 terminal and the IN2 terminal are arranged adjacentto each other. Here, the two terminals may be arranged in the reverseorder. Here, it is desirable to design these two external terminals(IN1, IN2) to have high withstand voltages so that they can withstandconnection to the power source E.

On the other hand, it is basically sufficient for the external terminals(SET1, SET2, OUT1, OUT2, GND) other than the above-mentioned twoterminals to be designed to have low withstand voltages. However, as tothe external terminal (GND) adjacent to the two external terminals (IN1,IN2) mentioned above, it is desirable, as a measure against a shortcircuit between adjacent terminals, to design the external terminal(GND) to have a high withstand voltage.

That is, it is desirable to select, as an external terminal to bearranged adjacent to the above-mentioned two external terminals (IN1,IN2), an external terminal (for example, GND) that is comparatively easyto design to have a high withstand voltage.

<Vehicle (Motorcycle, Four-Wheeled Automobile)>

FIG. 15 is an external view of a motorcycle. A motorcycle A shown inthis figure is an example of what is called a medium-sized motorcycle(=corresponding to an ordinary motorcycle defined, in the Road TrafficLaw of Japan, as belonging to the class of motorcycles with enginedisplacement over 50 cc but not over 400 cc). The motorcycle A has LEDlamp modules A1 to A3 (more specifically, an LED headlamp module A1, anLED rear-lamp module A2, and LED blinker-lamp modules A3), and a batteryA4 as a power source for these lamp modules.

FIG. 16 is an external view of a four-wheeled automobile. A four-wheeledautomobile B shown in this figure has LED lamp modules B1 to B3 (morespecifically, LED headlamp modules B1, LED rear-lamp modules B2, and LEDblinker-lamp modules B3), and a battery B4 as a power source for theselamp modules.

For convenience of illustration, the mounting positions of the LED lampmodules A1 to A3 and B1 to B3 and the batteries A4 and B4 in FIGS. 15and 16 may be different from reality.

As has been discussed above, with the LED lamp module 1 (see FIG. 2,FIG. 4, and FIG. 6) using the LED driver IC 100 provided with the powerconsumption distribution function, no unnecessarily large printedcircuit board is necessary. Accordingly, the LED lamp module 1 can bepreferably used in any of the LED headlamp modules A1 and B1, the LEDrear-lamp modules A2 and B2, and the LED blinker-lamp modules A3 and B3,of which all have restrictions as to the board area.

<Additional Description A>

An additional description will be given in connection with FIG. 8A toFIG. 8D referred to previously. As to a first terminal for receiving afirst current from a power source and a second terminal for receiving asecond current from the power source via an external resistor, it ispreferable that these terminals be both provided on a first side of apackage.

Here, preferably, the first terminal is provided at one end of the firstside, and the second terminal is provided adjacent to the firstterminal.

Or, the second terminal may be provided at one end of the first side,and the first terminal may be provided adjacent to the second terminal.

On the first side, in addition to the first and second terminals, theremay further be provided a third terminal that is connected to the powersource.

On the first side, in addition to the first to third terminals, theremay further be provided a fourth terminal that is not connected to thepower source.

Further, preferably, a fifth terminal for outputting a current to a loadis provided on a second side of four sides of the package, the secondside being a side different from the first side.

Here, preferably, the second side is a side that is opposite to thefirst side.

As the fifth terminal, a plurality of fifth terminals may be provided.

Preferably, the plurality of fifth terminals are provided adjacent toeach other.

Preferably, the fifth terminal is provided at one end of the secondside.

Further, preferably, a sixth terminal for connecting a ground terminalis provided next to the fifth terminal.

Further, preferably, a seventh terminal for heat dissipation is providedon the rear face of the package.

<Additional Description B>

Next, an additional description will be given in connection with FIG. 9to FIG. 13 referred to previously. It is preferable that a currentdistributor and a current driver be arranged separate from each othersuch that one is arranged on a first-side side of a semiconductor chipand the other is arranged on a second-side side of the semiconductorchip.

Here, preferably, a plurality of constant current sources included inthe current driver are arranged in a direction along the second side ofthe semiconductor chip in plan view of the semiconductor chip.

Further, preferably, in plan view of the semiconductor chip, the currentdistributor is integrated at a position between a position adjacent tosuch a constant current source of the plurality of constant currentsources as is located closest to a third side of the semiconductor chipand a position adjacent to such a constant current source of theplurality of constant current sources as is located farthest from thethird side.

Further, preferably, an other-circuit portion is integrated in a regionadjacent to both the current distributor and the current driver in planview of the semiconductor chip, the other-circuit portion including areference power supply configured to generate an internal referencevoltage, a CR timer for PWM (pulse width modulation) controlling anoutput current fed to the load, a protect bus controller configured toexchange fault signals with outside the device, various protectioncircuits, etc.

Further, preferably, in plan view of the semiconductor chip, the currentdistributor is integrated at a position between a plurality of partsinto which the other-circuit portion is divided.

Further, preferably, in plan view of the semiconductor chip, at leastpart of the other-circuit portion is integrated at a position betweenthe plurality of constant current sources.

Preferably, the current distributor, the current driver, and theother-circuit portion are arranged on a third-side side, and acontroller configured to integrally control the operation of thesemiconductor chip and a current setter configured to set the currentvalue of an output current fed to a load are arranged on a fourth-sideside, the third side and the fourth side being opposite to each other.

Here, preferably, the current setter is located closer to the fourthside than the controller.

As to a transistor constituting the current distributor, preferably afirst pad connected to a source region is arranged on the first-sideside, and a pad connected to a drain region is arranged on thethird-side side.

Preferably, a first wire via which the first pad and the first terminalare connected with each other is shorter than a second wire via whichthe second pad and the second terminal are connected with each other.

Preferably, in plan view of the semiconductor chip, the first wireextends from the first pad in a direction parallel to the third side tobe connected with the first terminal, and the second wire extends fromthe second pad in the direction parallel to the third side to beconnected with the second terminal.

<Additional Description C>

Next, an additional description will be given in connection with FIG. 14referred to previously. It is preferable to provide, on one side of apackage, all terminals including a first terminal for receiving a firstcurrent from a power source and a second terminal for receiving a secondcurrent from the power source via an external resistor.

Here, preferably, the second terminal is provided at one end of the oneside of the package and the first terminal is provided adjacent to thesecond terminal.

Or, the first terminal may be provided at the one end of the one side ofthe package and the second terminal may be provided adjacent to thefirst terminal.

Preferably, a third terminal for connecting a ground end is providedadjacent to the first or second terminal.

Preferably, the third terminal is provided between the first or secondterminal and a fourth terminal for outputting a current to a load.

As the fourth terminal, a plurality of fourth terminals may be provided.

Preferably, the plurality of fourth terminals are provided adjacent toeach other.

Preferably, at the other end of the one side of the package, a fifthterminal is provided which is not connected to the power source.

Other Modified Examples

The above-discussed embodiments have dealt with examples where thepresent invention is applied to a multi-channel LED driver IC. However,the application target of the present invention is not limited to amulti-channel LED driver IC at all, and the present invention is widelyapplicable to load drive devices in general where power consumptionneeds to be restricted.

The above-discussed embodiments have dealt with, as examples,configurations where an LED is used as a light emitting element, but,for example, it is also possible to use an organic EL(electro-luminescence) element as a light emitting element.

Thus, in addition to the above embodiments, it is possible to addvarious modifications to the various technical features disclosed hereinwithout departing from the spirit of the technological creation. Inother words, it should be understood that the above embodiments areexamples in all respects and are not limiting; the technological scopeof the present invention is not limited to the above description of theembodiments; and all modifications within the scope of the claims andthe meaning equivalent to the claims are covered.

INDUSTRIAL APPLICABILITY

The invention disclosed herein is usable, for example, in amulti-channel LED driver IC incorporated in an LED lamp module forvehicles (motorcycles, four-wheeled automobiles, etc.).

LIST OF REFERENCE SIGNS

-   -   1 electric appliance (LED lamp module)    -   100 load drive device (multi-channel LED driver IC)    -   110 current distributor    -   111, 112 P-channel MOS field-effect transistor    -   120 controller    -   121 input detector    -   121 a resistor    -   121 b current source    -   122 output detector    -   123 differential amplifier    -   130 current driver    -   131 to 134 constant current source    -   140 current setter    -   150 other-circuit portion    -   200 semiconductor chip    -   201 first side    -   202 second side    -   203 third side    -   204 fourth side    -   A motorcycle (vehicle)    -   B four-wheeled automobile (vehicle)    -   A1, B1 LED headlamp module    -   A2, B2 LED rear-lamp module    -   A3, B3 LED blinker-lamp module    -   A4, B4 battery    -   D drain region    -   E power source (battery)    -   IN1, IN2 input terminal    -   L1 conductor (current path)    -   OUT, OUT1 to OUT4 output terminal    -   P11 pad (source pad)    -   P12 pad (drain pad)    -   P31, P32, P33, P34 pad    -   R external resistor    -   S source region    -   W1, W2 wire    -   Z load (LED light source)    -   Z1 to Z4 LED string

1. A load drive device comprising: a first input terminal for acceptingan input of a first input current from a power source; a second inputterminal for accepting an input of a second input current from the powersource via an external resistor; an output terminal for outputting anoutput current to a load; a current distributor configured to generatethe output current by summing the first input current and the secondinput current at a prescribed distribution ratio; and a controllerconfigured to control the distribution ratio.
 2. The load drive deviceaccording to claim 1, wherein the current distributor includes a firsttransistor in a path in which the first input current flows, and thecontroller is configured to control an on-resistance value of the firsttransistor.
 3. The load drive device according to claim 2, wherein thecurrent distributor further includes a second transistor in a path inwhich the second input current flows, and the controller is configuredto differentially control on-resistance values of the first transistorand the second transistor.
 4. The load drive device according to claim1, wherein the controller is configured to control the distributionratio according to a difference value between a first terminal voltageappearing at the second input terminal and a second terminal voltageappearing at the output terminal.
 5. The load drive device according toclaim 4, wherein the controller includes an input detector configured togenerate a first differential input voltage from the first terminalvoltage, an output detector configured to generate a second differentialinput voltage from the second terminal voltage, and a differentialamplifier configured to generate a control signal for the currentdistributor according to a difference value between the firstdifferential input voltage and the second differential input voltage. 6.The load drive device according to claim 5, wherein the input detectoris configured to generate the first differential input signal bysubtracting a prescribed threshold voltage from the first terminalvoltage.
 7. The load drive device according to claim 5, wherein theoutput detector is configured to output a highest value of a pluralityof the second terminal voltages as the second differential input signal.8. The load drive device according to claim 5, wherein the outputdetector is configured to output an average value of a plurality of thesecond terminal voltages as the second differential input signal.
 9. Theload drive device according to claim 1, wherein the controller isconfigured to control the distribution ratio according to a differencevalue between a terminal voltage appearing at the second input terminaland a prescribed reference voltage.
 10. The load drive device accordingto claim 1, the load drive device further comprising a current driverconfigured to perform constant current control of the output current.11. The load drive device according to claim 10, wherein, in plan viewof a semiconductor chip, the current distributor is integrated on afirst-side side of the semiconductor chip, and the current driver isintegrated on a second-side side of the semiconductor chip opposite tothe first-side side of the semiconductor chip.
 12. The load drive deviceaccording to claim 11, wherein the current driver includes a pluralityof constant current sources respectively connected between the currentdistributor and a plurality of the output terminals.
 13. The load drivedevice according to claim 12, wherein, in plan view of the semiconductorchip, the plurality of constant current sources are arranged in adirection along the second side of the semiconductor chip.
 14. The loaddrive device according to claim 13, wherein, in plan view of thesemiconductor chip, the current distributor is integrated between aposition adjacent to such a constant current source of the plurality ofconstant current sources as is located closest to a third side of thesemiconductor chip and a position adjacent to such a constant currentsource of the plurality of constant current sources as is locatedfarthest from the third side of the semiconductor chip.
 15. The loaddrive device according to claim 1, wherein a terminal connected to thepower source and a terminal adjacent to the terminal have withstandvoltages sufficient to withstand connection to the power source.
 16. Theload drive device according to claim 2, wherein the first transistorincludes: a source region, a source pad provided immediately close tothe source region and wirebonded to the first input terminal, a drainregion, and a drain pad provided immediately close to the drain regionand wirebonded to the second input terminal.
 17. The load drive deviceaccording to claim 1, wherein the first input terminal and the secondinput terminal are arranged adjacent to each other.
 18. The load drivedevice according to claim 1, wherein, an external terminal designable tohave a high withstand voltage more easily than other external terminalsis arranged adjacent to the first input terminal or the second inputterminal.
 19. The load drive device according to claim 1, wherein thefirst input terminal accepts the input of the first input currentdirectly from the power source.
 20. The load drive device according toclaim 1, wherein the controller is configured to dynamically control thedistribution ratio.
 21. The load drive device according to claim 1,wherein the load drive device is integrated in a semiconductor device.22. The load drive device according to claim 2, wherein the controlleris configured to dynamically control the on-resistance value of thefirst transistor.
 23. The load drive device according to claim 3,wherein the controller is configured to dynamically differentiallycontrol the on-resistance value of each of the first transistor and thesecond transistor.
 24. The load drive device according to claim 4,wherein the controller is configured to dynamically control thedistribution ratio according to the difference value between the firstterminal voltage and the second terminal voltage.
 25. An electricappliance comprising: the load drive device according to claim 1; anexternal resistor connected between a first input terminal and a secondinput terminal of the load drive device; and a load connected to anoutput terminal of the load drive device.
 26. A lamp module comprising:the load drive device according to claim 1; an external resistorconnected between a first input terminal and a second input terminal ofthe load drive device; and a light source connected as a load to anoutput terminal of the load drive device.
 27. A vehicle comprising: thelamp module according to claim 26; and a battery as a power source forthe lamp module.
 28. The vehicle according to claim 27, wherein the lampmodule is a headlamp module, a rear-lamp module, or a blinker-lampmodule.